It has conventionally been proposed to decrease air permeability of an inner liner of a tire to reduce thickness of the inner liner, so that tire weight and fuel consumption of the tire are reduced accordingly. For example, use of a rubber composition containing lower-grade carbon black at a high blending content for an inner liner has been proposed to reduce thickness of the inner liner. However, the resulting inner liner has problems in terms of flex (bending) resistance and durability at low temperature in this case.
As another conventionally known example, it is possible to reduce air permeability of an inner liner, while maintaining good flex and durability at low temperature of the inner liner, by using a rubber composition containing non-reinforcible flat mica and/or clay blended therein for the inner liner. Specifically, PTL 1 discloses a rubber composition for an inner liner of a pneumatic tire, produced by blending 100 parts by weight of solid state rubber with 1-150 parts by weight of organically treated layer state clay mineral. Further, PTL 2 discloses a rubber composition for an inner liner of a pneumatic tire, comprising a rubber component and a lamellar or flaky mineral having an aspect ratio of 3 to 30 (inclusive of 3 and exclusive of 30).